Reddit Coding Interview Questions
100 Reddit coding interview problems with full optimal solutions — 34 easy, 52 medium, 14 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Reddit interviewer values, and a FAQ section.
Showing 3 problems of 100
- #89hardfrequently asked
89. Merge k Sorted Lists
Merge k sorted linked lists into one sorted list. Reddit uses this to test heap-based merging — the exact shape used when merging hot/new/rising/controversial ranked streams into a single user feed.
- #95hardfrequently asked
95. Trapping Rain Water
Compute how much rain water is trapped between elevation bars. Reddit uses this to test two-pointer + min/max tracking — the same shape used to identify dips between vote-volume peaks in their popularity-decay analysis.
- #100hardfrequently asked
100. Minimum Window Substring
Find the smallest substring of s containing all chars of t. Reddit uses this sliding-window hard problem to test the contract-and-expand pattern — the same shape used when searching for the smallest active vote-window covering a target user-set during fraud audits.